Design of Anchors in Seismic Regions as per the New ... · PDF filethe anchor hole (notch...

Seismic Academy I Bologna 8 Novembre 2013 | J. Gramaxo 1 www.hilti.it/sismico

Hilti Seismic Academy

Jorge Gramaxo

Technical Marketing

Hilti AG

Design of Anchors in Seismic Regions as per the New European Guideline EOTA TR045


• When cracks form in concrete, there is a high chance that they will

intersect the anchor location considering:

Anchors are expected to be located in concrete

cracks during an earthquake

stresses from the pre-stressing

or loading of the anchor

stress concentration caused by

the anchor hole (notch effect)

Source: Prof. Rolf Eligehausen , University of Stuttgart: tests to asses the likelihood of cracks intercepting the position of

anchors and anchor holes


• As a cracks intersect the anchor the load transfer will be changed due

to an unsymmetrical distribution of the anchor loads

• The resistance of the anchors is highly affected by the width of the

cracks and in case of earthquake loading can reach 0.8mm

Concrete cracks lead to significant changes in

the anchors load transfer and performance

stress distribution in

non-cracked concrete

stress distribution in

cracked concrete

crack plane


• During an earthquake the anchors will be need to cope with:

Seismic loading induces extreme conditions in

the fastenings, much above concrete cracks S

hea

r T

ensio

n C

rack w

idth

Load cycling Concrete crack cycling

w/ larger crack width

Anchor design for seismic loading requires a set of specific

prequalification, approval document and design regulations


• Consistent with the new European assessment for anchors in seismic

regions, ETAG 001 Annex E, and applicable for anchors which have

been awarded an ETA in accordance to it.

• Has been developed during the revision of the CEN/TS 1992-4 series

and complies with the final draft of EN 1992-4

• This document intends to guide the design of anchor for seismic

loading bridging the time span until the publication of EN 1992-4

EOTA TR045 represents current best practice

for seismic design of anchors in Europe

< 2013

No EU regulation

2013

EOTA TR045

2014 / 2015

EN 1992-4

European design method for anchors to resist seismic loading


b) Ductile anchor

• anchors must fulfill the ductility requirements and

steel failure must govern the anchor resistance

To ensure ductile behavior of the connection

3 different design approaches are offered

a1) Capacity Design

• anchors must resist to the load corresponding to

the yielding or failure of the attachment

a2) Elastic design

• anchors must resist to the load resulting from an

elastic seismic design


Pragmatic approach for calculating of seismic

actions in non-structural elements

• As per Eurocode 8 can often be difficult to establish with confidence

the fundamental vibration period Ta of the non-structural element.

Fa = Sa . Wa / qa

• EOTA TR045 to solve this issue provides:

- expression from Eurocode 8 rearranged (equation 4.25, EN1998-1)

- seismic amplification factor Aa per non-structural element

- behavior factors qa for additional non-structural elements

Wa – own weight of the element (KN)


Tension resistance to seismic loading for

mechanical anchors

TENSION

Ref. values N0Rk,seis

ETA values

(C1 or C2) Calculated as per

ETAG 001 Annex C

Steel N0Rk,s,seis -

Pull-out N0Rk,p,seis -

Concrete cone - N0Rk,c,seis

NRk,seis = agap ∙ aseis ∙ N0

Rk,seis

aseis provided by the TR

agap = 1.0 (no influence in tension)

Nd,seis = Nk,seis / gM,seis gM,seis – provided by the ETA


Tension resistance to seismic loading for

chemical anchors

TENSION

Ref. values N0Rk,seis

ETA values

(C1 or C2) Calculated as per

EOTA TR029

Steel N0Rk,s,seis -

Combined pull-out and

concrete cone tRk,seis N0

Rk,p,seis

Concrete cone - N0Rk,c,seis

NRk,seis = agap ∙ aseis ∙ N0

Rk,seis


agap = 1.0 (no influence in tension)

Nd,seis = Nk,seis / gM,seis gM,seis – provided by the ETA


Shear resistance to seismic loading for

mechanical and chemical anchors

SHEAR

Ref. values V0Rk,seis

ETA values

(C1 or C2) Calculated as per ETAG

001 Annex C / TR029

Steel V0Rk,s,seis -

Pry-out - V0Rk,cp,seis

Concrete edge breakout - V0Rk,c,seis

VRk,seis = agap ∙ aseis ∙ V0

Rk,seis


agap = 1.0 filled annular gap

= 0.5 if annular gap is not filled

Vd,seis = Vk,seis / gM,seis gM,seis – provided by the ETA


Presence of annular gaps between the anchors

and the fixture reduces shear resistance to half

The shear forces on the anchors are amplified in presence an

annular gap due to a hammer effect on the anchor

• The factor agap attends to the overload resulting from annular gap

between the anchor and the steel plate

• Design shear resistance x2 if it can be ensured no hole clearance

between the anchor and the fixture.

• Hilti Dynamic Set ensures proper filling of the annular gap and as such

ensures the an enhanced shear resistance under seismic loading


• If deformations are relevant for the connection it shall be demonstrated

that these deformations can be accommodated by the anchors

• Anchors awarded Seismic Performance Category C2 ETA’s provide the

anchor’s displacement for shear and tension

• If the required displacement is smaller than what the anchor displays,

then the following reduction is applied to the design resistance

Anchorage proof for the Damage Limitation

State (DLS) is also considered in EOTA TR045

dN,req (DLS) Defined by the designer ;

Note: Expression for the correction of tension design resistance; shear is done in the same manner

dN,seis (DLS) Provided in the relevant ETA


Summary of the seismic design procedure

Selected anchors by their Seismic Performance Category (C1 or C2)

according to the ground acceleration and building importance class

Identify the ULS seismic loads according to the suitable design approach

depending on your general design considerations

Calculate the seismic design resistances for N, V and load combination

considering the characteristic resistances from the ETA

If required, verify to DLS comparing required / anchor displacements

considering the loads for the DLS verification


Currently seismic approved Hilti solutions for

seismic performance category C1 and C2

Structural

application

Non-structural

application

ETA C2 ETA C1*

ETA C2

* For buildings class IV: C2 required

Source: Countries seismic acceleration maps ;

EOTA TR045 recommendations

HST / HST-R

C2:M10-M16 ; C1:M10-M16

HIT-HY 200 + HIT-Z

C2:M12-M16 ; C1:M8-M20

Seismic Category C2

http://www.google.pt/url?sa=i&rct=j&q=Hilti+HIT-Z&source=images&cd=&cad=rja&docid=kZolt7vctfS7BM&tbnid=bGj5C7MtVrBx_M:&ved=0CAUQjRw&url=http://www.forconstructionpros.com/press_release/10885367/hit-hy-200-adhesive-anchor-system&ei=oeaUUefZL4XJPJm3gPAJ&bvm=bv.46471029,d.Yms&psig=AFQjCNFn12h9xr3cKPqHE_kNXNz7NBgIMw&ust=1368799246216176


Hilti Seismic Academy

Jorge Gramaxo

Technical Marketing

Hilti AG

Thank you for your attention!

Design of Anchors in Seismic Regions as per the New ... · PDF filethe anchor hole (notch...

Documents

Transcript of Design of Anchors in Seismic Regions as per the New ... · PDF filethe anchor hole (notch...